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2001 | PATENTS
| INTERNET
| Arunajatesan
S., Carim A. H. Symmetry and Crystal Structure
of Ti3SiC2
// Mater. Lett. - 1994. - 20(5-6). - 319-324. Convergent beam electron diffraction (CBED) and x-ray diffractometry (XRD) were used to examine the symmetry, structure and lattice parameters of Ti3SiC2. The CBED anal. confirms that the material is hexagonal with a point group of 6/mmm. The XRD diffraction peak positions and intensities agree with calcns. based on previously proposed at. positions. |
| Chen
H. K., Lin C. I., Lee C. Kinetics of the Reduction
of Carbon / Alumina Powder Mixture in a Flowing Nitrogen Stream //
J. Am. Ceram. Soc. - 1994. - 77(7). - 1753-1756. The reduction of carbon / alumina powder mixture in a flowing nitrogen stream was investigated by wight loss measurement and X-ray diffraction. Experimental results indicated that the reaction rate could be increased by increasing the nitrogen flow rate, weight ratio of C / Al2O3, or reaction temperature. The rate was also found to be increased by decreasing the sample size, the grain sizes of carbon or alumina oxide, or initial bulk density. Empirical expressions of consumption rates of Al2O3 and C as well as production rate of AlN have been determined. |
| Komarenko
P., Clark D. E. Synthesis of Ti3SiC2-based
Materials Using Microwave-Initiated SHS //
Ceram. Eng. Sci. Proc. - 1994. - 15(5). - 1028-35. Prepn. and characterization of ceramic materials in the Ti-Si-C system are presented. Mixts. of titanium, silicon and carbon powders were ignited by microwave energy. Powders prepd. by conventional SHS and microwave-initiated SHS were compared. Compositional characteristics of these powders were detd. using X-ray diffraction. Conventionally-ignited SHS compacts, with no sustainable heating after ignition, resulted in a product with a large fraction of TiC. Conventionally-ignited SHS samples that were sustainably heated for up to 30 min at 1400-1450° resulted in a product composed of TiC with traces of Ti3SiC2. Samples ignited and sustainably heated with microwave energy for up to 30 min at 1400-1450° resulted in a product that maintained a high fraction of the Ti3SiC2 phase. Microwave energy seemed to inhibit the decompn. and actually favor the formation of the Ti3SiC2 phase starting from Ti-Si-C powder mixts. |
| Lihrmann J.-M. SiCAlON Ceramics / Encyclopedia
of Advanced Materials. Vol. 4. - Pergamon Press, 1994. - 2451-2454. [no abstract] |
| Lis J., Pampuch R. Sinterable Ceramic Powders Prepared
by SHS, Their Densifications and Final Products // Trans. Mater.
Res. Soc. Jpn. - 1994. - 14A. - 603-608. [no abstract] |
| Lis J. Sinterable Powders of Covalent Compounds Prepared by Self-Propagating High-Temperature Synthesis (SHS) / Pr. Kom. Nauk Ceram., Ceram. (Pol. Akad. Nauk). - 44. - 1994. (Polish). |
| Okano
T., Yano T., Iseki T. Synthesis and Mechanical
Properties of Ti3SiC2
Ceramic // Trans. Mater. Res. Soc. Jpn.. -
1994. - 14A. - 597-600. [no abstract] |
| Racault
C., Langlais F., Bernard C. On the Chemical
Vapor Deposition of Ti3SiC2
from TiCl4-SiCl4-CH4-H2
Gas Mixtures. Part I. A Thermodynamic Approach
// J. Mater. Sci. - 1994. - 29(19). - 5023-5040. In the ternary system Ti-Si-C, the ternary compd. Ti3SiC2 seems to exhibit promising thermal and mech. properties. Its synthesis as a thin film from the vapor phase is very difficult owing to the complexity of the system. A contribution to the knowledge of the chem. vapor deposition of Ti3SiC2 from a TiCl4-SiCl4-CH4-H gas mixt. is proposed on the basis of a thermodn. approach. This approach is based on a reliable estn. of Ti3SiC2 thermodn. data in good accordance with recent exptl. results on its thermal stability. A first equil. calcn. for the deposition on an inert substrate shows the influence of the exptl. parameters on the compn. of both the deposit and the gas phase. As a result, the deposition of Ti3SiC2 can be favored by an excess of TiCl4 (.gtoreq.45%), a rather low pressure (10-20 kPa), high temp. (>= 1273 K), and low H diln. ratio. On the basis of equil. calcns. for various substrates, complex mechanisms of Ti3SiC2 deposition are pointed out, with intermediate steps of substrate consumption, e.g., the formation of TiC from a C substrate or TiSi2 from a Si substrate. |
| Racault
C., Langlais F., Naslain R., Kihn Y. On the
Chemical Vapor Deposition of Ti3SiC2
from TiCl4-SiCl4-CH4-H2
Gas Mixtures. Part II. An Experimental Approach //
J. Mater. Sci. - 1994. - 29(15). - 3941-3948. An exptl. study of the deposition of Ti3SiC2-based ceramics from TiCl4-SiCl4-CH4-H2 gaseous precursors is carried out under conditions chosen on the basis of a previous thermodn. approach, i.e., a temp. of 1100 °C, a total pressure of 17 kPa, various initial compns. and substrates of silicon or carbon. Ti3SiC2 is deposited within a narrow compn. range and never as a pure phase. A two-step deposition process is obsd., in agreement with the thermodn. calcns. For a silicon substrate, TiSi2 is formed as an intermediate phase from consumption of Si by TiCl4 and then is carburized by CH4 into Ti3SiC2. For a carbon substrate, the first step is the formation of TiCx either from consumption of carbon by TiCl4 or by reaction between TiCl4 and CH4 and then TiCx reacts with the gaseous mixt. to give rise to Ti3SiC2. In most cases, Ti3SiC2 is obtained as small hexagonal plates oriented perpendicular to the substrate surface. These nano- or micro-crystals are usually co-deposited with TiCx and to a lesser extent SiC, and their size is increased by increasing the diln. of the gaseous mixt. in hydrogen. |
| Racault
C., Langlais F., Naslain R. Solid-State Synthesis
and Characterization of the Ternary Phase of Ti3SiC2
// J. Mater. Sci. - 1994. - 29(13). - 3384-3392. Ti3SiC2 is the only true ternary compd. in the Ti-Si-C system. It seems to exhibit promising thermal and mech. behavior. With the exception of its layered crystal structure, most of its properties are unknown, owing to the great difficulty of synthesis. A new procedure of solid-state synthesis with several steps is proposed, which results in Ti3SiC2 with less than 5 at.% TiC. Ti3SiC2 is stable at least up to 1300 °C. Beyond this temp., it can decomp. with formation of non-stoichiometric titanium carbide and gaseous silicon, with kinetics highly dependent on the nature of the surroundings. As an example, graphite can initiate this process by reacting with silicon, while alumina does not favor the decomp. which remains very slow. The oxidn. of Ti3SiC2 under flowing oxygen starts at 400 °C with formation of anatase-type TiO2 film, as studied by TGA, XRD, SEM and AES. At 650-850 °C, both rutile and anatase are formed, rapidly forming protective films and giving rise to slow formation of SiO2 and more TiO2. The oxidn. kinetics is slower than for TiC, owing to a protecting effect of silica. By increasing the temp., both oxidn. processes (i.e. direct reaction and diffusion through oxide layers) are activated and an almost total oxidn. is achieved at 1050-1250 °C resulting in titania (rutile) and silica (cristobalite). |
| Schneider
A. , Schober R. New Materials in the AlCON-System
/ International Conference Ceramic Processing Science and Technology,
11-14.09.1994, Friedrichshafen (Germany). [html (Poster located on web-site of Fraunhofer Institute of Ceramic Technologies and Sintered Materials)] |
| Tamai
F., Naka M. The Role of Ti in SiC / SiC Joint
Brazed with Cu-Ti Fillermetals // Trans. Mater. Res. Soc. Jpn.
- 1994. - 16B. - 1113-1116. [no abstract] |
| Tsuchida
T., Hasegawa T., Inagaki M. Self-Combustion
Reaction Induced by Mechanical Activation: Formation of Aluminum Nitride
from Aluminum - Graphite Powder Mixture // J. Am. Ceram. Soc.
- 1994. - 77(12). - 3227-3231. The powders of aluminum metal and natural graphite mixed in various molar ratios (Al / C = 7/0 - 0/7) were ground in a planetary ball mill. When the mixtures thus activated mechanically were exposed to air, exothermic reactions spontaneously occurred in two successive steps, evolving red heat initially and then white heat. The main product was aluminum carbide in the first step and aluminum nitride as well as carbide in the second step. From the measurements of XPS spectra and the lattice constants, it was concluded that the aluminum nitride obtained is solid solution with the composition of (Al2OC)1-x(AlN)x. The effects of mixing ratio of Al to C, grinding time, and gas atmosphere on the formation of aluminum nitride are discussed. |
| Ustichenko
V.A., Chistyakov A. A. Fused Material Based
on Alumina and Carbon // Ogneupory. - 1994. - 3. - 2-7. (Russian). [no abstract] |
| Vardiman
R. G. Temperature-Induced Phase Development
in Titanium-Implanted Silicon Carbide // Mater. Sci. Eng. A
- 1994. - 177(1-2). - 209-215. Silicon carbide has been implanted with titanium at three different doses. TEM and RBS have been used to follow changes resulting from post-implantation heat treatment. The as-implanted layer is amorphous, and after a low temp. anneal a fine, nonequil. titanium carbide ppt. appears in the amorphous matrix. At higher temps., the ternary phase Ti3SiC2 and the SiC crystallize. The initial Gaussian titanium concn. profile changes near the ternary phase pptn. temp., developing side peaks at the area of max. initial concn. gradient. Thermodn. and kinetic factors in the obsd. phase development are discussed, and the need for a metastable phase diagram is considered. |
